Method for transmitting encrypted packet in communication system

ABSTRACT

Provided is a method for transmitting a packet in a communication system, comprising the steps of: identifying the packet according to a packet identification criterion; reallocating frames included in the identified packet and encrypting the packet in which the frames have been rearranged; and transmitting the encrypted packet

BACKGROUND OF THE INVENTION Field of the Invention

Example embodiments relate to a method of selectively reallocating videopackets based on an significance in the range of video frames, forexample, a group of pictures, having a cross-reference relationship, andselectively performing an encrypted transmission and a non-encryptedtransmission of the reallocated video packets based on an significanceto resolve issues, for example, an illegal image acquisition andexposure of personal information, which may occur during a videotransmission on a mobile device with limited available resources.

Description of the Related Technology

Recently, the amount of mobile video uses is continuously increased suchas YouTube, personal broadcasting, and real-time surveillance. Inparticular, the video usage of remote surveillance devices, which arerepresented by closed-circuit television (CCTV), is significantlyincreasing due to the admissibility of evidence in court.

However, because the remote surveillance devices having been operated inan existing closed network are connected to a public network, such asthe Internet, for system management and user convenience, there areconcerns about issues, such as an illegal image acquisition by anunauthorized third party when transmitting an acquired image andexposure of personal information. For example, if an operation right ofa remote surveillance device is hacked through the Internet, a controlright for a system of the corresponding remote surveillance device canbe acquired, an acquired image and a transmission target of the acquiredimage may be arbitrarily manipulated. Also, although a system operationright is not acquired, an image may be acquired through eavesdropping ona video being transmitted. In this case, the image may be continuouslyaccessed without trace of intrusion from a corresponding device. Inparticular, in a case in which the image is acquired througheavesdropping, the seriousness may further grow in that a method oftransmitting data wirelessly using a broadcasting scheme is generallyemployed and an image may be acquired from an unmanned arterial vehicle(UAV) operated by an army or a public CCTV of a daycare center, usingsimple monitoring equipment.

To prevent this, a number of video transmission schemes have beenproposed with full or partial encryption of target video. Herein,encryption refers to converting the target video to a format that cannotbe viewed by an unauthorized third party, using an encryption algorithm,such as, an advanced encryption standard (AES).

Initially, a full video encryption method provides the highest level ofsecurity. However, a large amount of computing power is required for theencryption, which may significantly increase according to an increase ina size of an image to be transmitted. Accordingly, many remotesurveillance devices, such as, an unmanned drone and a CCTV, havingrelatively low-computing power transmit an image without using anencryption process.

To outperform the issues found in the full video encryption method, aselective encryption methods for selectively encrypting important datathrough a video analysis have been proposed. However, the existingproposed selective encryption methods may have the followingconstraints. Initially, the selective encryption method has a relativelylow level of security compared to the full video encryption method sinceonly a specific portion is encrypted and transmitted due to the limitedcomputing power of a mobile device. In particular, if a size of data tobe encrypted is inconstant, a stream-based encryption method, forexample, a stream cipher, needs to be used instead of using ablock-based encryption method, for example, a block cipher, which leadsto further degrading the security. Further, mobile devices have varioussystem specifications according to the purposes of the mobile devicesand have different computational power. Due to an encryptiontransmission characteristic of generating additional load in a system,an encryption transmission method suitable for the computational powerof each device is required. However, in the existing selectivetransmission methods, it is difficult to quantify a video to beencrypted and thus, the above suggestion may be inapplicable. Further,when an encryption target is to be selected by directly analyzing anencoded video, additional computational overhead is required. Whenencryption is to be performed by considering, for example, motionvectors, coefficients, and quantization parameters of a video, an amountof an original video to be analyzed for encryption increases.Considering that a “shoot-record-encrypt-transmit” function is generallyperformed in a single remote surveillance device, a decrease inadditional computational load is important for a smooth operation ofsurveillance devices.

SUMMARY EXAMPLES

Example embodiments provide a packet transmission method of acommunication system that may identify a packet based on headerinformation of the packet and may selectively encrypt the packet basedon an importance of the identified packet.

Example embodiments also provide a packet transmission method of acommunication system that may selectively encrypt the identified packetbased on header information, and an available resource amount of acommunication system.

Example embodiments also provide a packet transmission method of acommunication system that may selectively rearrange frames having across-reference relationship among the entire frames included in apacket.

Example embodiments also provide a packet reception method of acommunication system that may determine whether decryption of a packetis required and may selectively decrypt the packet based on a packetidentification criterion.

Solutions

According to an aspect, there is provided a packet transmission methodof a communication system, the method including identifying a packetbased on a packet identification criterion; reallocating frames includedin the identified packet, and encrypting the packet in which the framesare rearranged; and transmitting the encrypted packet.

According to an aspect, there is provided a packet reception method of acommunication system, the method including determining whetherdecryption of a packet is required based on a packet identificationcriterion of the packet; decrypting the packet based on the packetidentification criterion when the decryption of the packet is determinedto be required; and reallocating frames of the packet.

According to an aspect, there is provided a packet transmissionapparatus of a communication system, including a processor configured todetermine whether to perform a packet identification process or a packetencryption process based on a remaining system resource amount and toidentify a packet based on a packet identification criterion when thepacket identification process and the packet encryption process aredetermined to be performed; an encoder configured to rearrange frames ofthe packet based on a result of identifying the packet and to encryptthe packet in which the frames are rearranged; and a transmitterconfigured to transmit the encrypted packet.

Effect

According to example embodiments, it is possible to effectively copewith issues, such as an illegal image acquisition by a third party andexposure of personal information, which may occur during a videotransmission, based on an available resource amount of a mobile device.

Also, according to example embodiments, if a video observes a networkabstraction layer (NAL) header standard defined in image standards,H.264/advanced video coding (AVC) and high efficiency video coding(HEVC)/H.265 standards, and also observes a packet header format definedin an MPEG-2 transport stream (TS) standard, independent application maybe performed without modifying existing software and hardware products.

Also, according to example embodiments, application may be performed foran imaging module of an unmanned aerial vehicle (UAV), an imagetransmission of a closed-circuit television (CCTV) connected to awired/wireless network, a broadcasting image acquired using a mobiledevice, a video conference using a personal device, and also may beperformed in various fields, for example, a communication, a multimediatransmission and reception, and networking.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating an encrypted packet transmissionmethod of a communication system according to an example embodiment.

FIG. 2 illustrates an example of classifying an important video packetin the case of observing a network abstraction layer (NAL) headerstandard defined in an H.264/advanced video coding (AVC) standard and ahigh efficiency video coding (HEVC)/H.265 standard, and also observing apacket header format defined in an MPEG-2 transport stream (TS) standardaccording to an example embodiment.

FIGS. 3 and 4 illustrate examples of an operation of encrypting a packetin an encrypted packet transmission method of a communication systemaccording to an example embodiment.

FIG. 5 is a flowchart illustrating an operation of selectivelyreallocating video packets based on an importance when determining avideo packet according to an example embodiment.

FIG. 6 is a flowchart illustrating an operation of controlling anencryption target video based on an available resource amount whentransmitting a video packet to which an encrypted packet transmissionmethod of a communication system is applied according to an exampleembodiment.

FIGS. 7 and 8 are flowcharts illustrating an operation of decoding apacket in an encrypted packet reception method of a communication systemaccording to an example embodiment.

FIG. 9 is a block diagram illustrating a configuration of a packettransmission apparatus of a communication system according to an exampleembodiment.

FIG. 10 is a block diagram illustrating a configuration of a packetreception apparatus of a communication system according to an exampleembodiment.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS Best Mode

Various modifications may be made to the example embodiments. However,it should be understood that these embodiments are not construed asbeing limited to the illustrated forms and include all changes,equivalents or alternatives within the idea and the technical scope ofthis disclosure.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms“comprise/include” and/or “have,” when used in this specification,specify the presence of stated features, integers, steps, operations,components, parts or combinations thereof, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, components, parts or combinations thereof.

Unless otherwise defined, all terms including technical and scientificterms used herein have the same meaning as commonly understood by one ofordinary skill in the art to which these example embodiments belong. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Regarding the reference numerals assigned to the elements in thedrawings, it should be noted that the same elements will be designatedby the same reference numerals, wherever possible, even though they areshown in different drawings. Also, in the description of embodiments,detailed description of well-known related structures or functions willbe omitted when it is deemed that such description will cause ambiguousinterpretation of the present disclosure.

FIG. 1 is a flowchart illustrating an encrypted packet transmissionmethod of a communication system according to an example embodiment.

In operation S110, the packet transmission method may identify a packetbased on a packet identification criterion. The packet identificationcriterion may be recognized as the same concept as a packet identifieron the communication system and may indicate each of identifiersassigned to packets in a multiplexed transmission flow, respectively.When multiplexing and transmitting a plurality of channel signals usinga single transmission line, the communication system may independentlycompress and packetize each of the channel signals and then maymultiplex packets and transmit the multiplexed packets. Here, the samepacket identifier (PID) may be assigned to a packets corresponding to asingle channel to be distinguished from a packets of another channel.

In operation S120, the packet transmission method may rearrange framesincluded in the identified packet and may encrypt the packet in whichthe frames are rearranged. In operation S130, the packet transmissionmethod may transmit the encrypted packet. Once an identified specificpacket is encrypted, encryption transmission may be performed byapplying an encryption protocol, for example, a secure sockets layer(SSL) protocol or an encryption algorithm, for example, an advancedencryption standard (AES) algorithm. Non-encryption transmission may beperformed on a packet corresponding to a packet identification criterionthat does not require encryption transmission. Packet rearrangement andencryption will be further described with reference to FIG. 5.

FIG. 2 illustrates an example of classifying an important video packetin the case of observing a network abstraction layer (NAL) headerstandard defined in an H.264/advanced video coding (AVC) standard and ahigh efficiency video coding (HEVC)/H.265 standard, and also observing apacket header format defined in an MPEG-2 transport stream (TS) standardaccording to an example embodiment.

Referring to FIG. 2, according to an example embodiment, a packetidentification criterion may be associated with header information of apacket. According to another example embodiment, the packetidentification criterion may be associated with a level of securityrequired for transmission of the packet. A packet encryption method of acommunication system according to an example embodiment may assign arelatively high importance to metadata associated with video streamingand metadata associated with encoded video and verifiable based on avideo packet unit, and may assign a relatively high importance, forexample, a first type packet and a second type packet, to an encodedvideo packet that stores complete scene information, such as I-framedata. In addition, the packet encryption method may assign a relativelylow importance, for example, a (n−1)^(th) type packet and an n^(th) typepacket, to other video packets, for example, video packets that arereferred to by a portion of other frames or not referred to. Accordingto an example embodiment, the header information may be compatible withat least one of a NAL header format of an H.264/AVC standard and a NALheader format of an HEVC/H.265 standard, and may be compatible with aheader format of an MPEG-2 TS standard. Classification of importantvideo packets may be used to classify metadata information, such as aprogram association table (PAT) or a program mapping table (PMT), basedon process ID (PID) information that is included in an MPEG-2 TS packetheader, or to classify media presentation description (MPD) and a videoframe header, etc., based on Nal_Ref_Idc (NRI) and Nal_Unit_Type (NUT)information of a NAL header defined in H.264/AVC or HEVC/H.265.

FIGS. 3 and 4 illustrate examples of an operation of encrypting a packetin an encrypted packet transmission method of a communication systemaccording to an example embodiment.

Referring to FIG. 3, in operation S310, the packet transmission methodmay rearrange locations of frames so that frames including a data areaof a packet are positioned to be adjacent to each other among the entireframes included in a cross-reference range. Referring to

FIG. 4, the entire frames included in the cross-reference range arearranged, and frames included in an (m+1)^(th) IP packet and an(m+2)^(th) IP packet are arranged without considering a priority.Compared to a before-rearrangement, after a rearrangement, packetshaving a relatively high priority may be arranged as the (m+1)^(th) IPpacket and packets having a relatively low priority may be arranged asthe (m+2)^(th) IP packet. During the above process, there is no need torearrange all of the packets and the packets may be selectivelyrearranged based on an importance of a packet.

Referring again to FIG. 3, in operation S320, the packet transmissionmethod may store the rearranged frames in a storage space for a frametransmission. As described with FIG. 4, once packets having a relativelyhigh priority are rearranged, the rearranged packets may be stored inthe same storage space, such as a buffer or a memory, so that a packetmay be transmitted based on a unit of frames having a cross-referencerelationship. The packet stored in the storage space may be transmittedthrough a transmitter.

FIG. 5 is a flowchart illustrating an operation of selectivelyreallocating video packets based on an importance when determining avideo packet according to an example embodiment.

According to an example embodiment, an operation of identifying a packetbased on a packet identification criterion may include an operation ofdetermining a priority of the packet by verifying a value of an MPEG-2TS header and a value of a NAL header. Referring to FIG. 5, once aprocessor receives video packets, the processor may write a serialnumber to each of the video packets for order restoration. The processormay read the video packets one by one and may perform a process ofdetermining a type of a corresponding packet. To this end, the processormay check a process ID (PID) value of a packet header defined in anMPEG-2 TS standard and may verify whether the packet includesinformation corresponding to a PAT or a PMT.

According to an example embodiment, an operation of reallocating framesincluded in the identified packet and encrypting the packet in which theframes are rearranged may include an operation of storing the packet ina transmission buffer when the determined priority is greater than adesired value and storing the packet in a flush buffer when thedetermined priority is less than the desired value. When the read videopacket corresponds to the PAT or the PMT, and in this instance, thevideo packet has a relatively high importance based on a parameter thatstores the importance of the video packet, that is, a value assigned toa priority, the video packet may be duplicated to the transmissionbuffer. When the video packet has a relatively low importance, the videopacket may be duplicated to the flush buffer. When the read packet doesnot correspond to the PAT or the PMT, a Nal_Ref_Idc (NRI) value of a NALheader defined in H.264/AVC and HEVC/H.265 may be checked. If the NRIvalue is 3, a Nal_Unit_Type (NUT) value of the NAR header may be checkedagain. When a current packet is determined to include a header of anI-frame based on the NUT value, a relatively high value may be assignedto a priority parameter and video packets of the flush buffer may beduplicated to the transmission buffer. Subsequently, the read videopacket maybe duplicated to the transmission buffer. If the NRI value isnot 3, the currently read video packet may be duplicated to thetransmission buffer. A subsequently located single packet may be readfrom a reception buffer. The flow of FIG. 4 may be repeated untilreception of a video packet is terminated.

FIG. 6 is a flowchart illustrating an operation of controlling anencryption target video based on an available resource amount whentransmitting a video packet to which an encrypted packet transmissionmethod of a communication system is applied according to an exampleembodiment.

According to an example embodiment, the encrypted packet transmissionmethod of the communication system may read rearranged and therebystored video packets from a storage space and may identify videoinformation corresponding to a start point of a unit of video frameshaving a cross-reference relationship. To this end, informationcorresponding to a header of an I-frame may be used based on payloadunit start indicator (PUSI) information included in an MPEG-2 TS packetheader and NRI and NUT information of a NAL header defined in H.264/AVCor HEVC/H.265 Important video packets requiring encryption transmissionmay be dynamically selected based on an available resource amount.

Referring to FIG. 6, a video packet transmitter may read video packetsfrom a reception buffer one by one, and may perform a process ofdetermining a type of a corresponding packet. To this end, the videopacket transmitter may check a PUSI value of a packet header defined inan MPEG-2 TS standard. If the PUSI value is zero and a packet type isnot P-frame or B-frame data, a current video packet may be duplicated toa transmission buffer. If the packet type is the P-frame or B-framedata, a relatively low value may be assigned to a priority parameter andzero may be assigned to a PB header counter parameter.

According to an example embodiment, an operation of identifying thepacket based on a packet identification criterion may include anoperation of determining a priority of the packet by verifying a valueof an MPEG-2 TS header and a value of a NAL header. If the PUSI value is1, an NRI value of an NAL header defined in H.264/AVC H.264/AVC andHEVC/H.265. If the NRI value is 3, an NUT value of the NAL header may bechecked. When a current packet is determined to include a header of anI-frame, a relatively high value may be assigned to a priorityparameter. In a normal situation in which an available resource amountis sufficient, video packets of the transmission buffer may betransmitted through an encryption protocol, for example, an SSLprotocol. In a situation in which the available resource amount isinsufficient, video packets of the transmission buffer may betransmitted through an encryption protocol, for example, a TCP. When thecurrent video packet is determined to not include the header of theI-frame and a relatively high value is determined to be assigned to thepriority parameter, the current video packet may be duplicated to thetransmission buffer. If the relatively low value is determined to beassigned, non-encryption transmission may be performed on video packetsof the transmission buffer.

If the NRI value is not 3, a PB header counter may increase by one andthe current video packet may be duplicated to the transmission buffer.

Once the current video packet is duplicated to the transmission bufferin each routine, whether a value of the PB header counter parameter is amaximum value may be verified. If the value of the PB header counterparameter matches the maximum value, the value of the BP header countermay be initialized to zero and a relatively low value may be assigned toa value of the priority parameter. For example, if a group of pictures(GOP) is set as 30, 29 corresponding to a total number of P-frames andB-frames excluding a single I-frame may be set as the maximum value.

If the value of the PB header counter parameter is not the maximumvalue, a number of video packets present in the transmission buffer maybe counted without performing the above process.

According to an example embodiment, an operation of reallocating framesincluded in the identified packet and encrypting the packet in which theframes are rearranged may include an operation of verifying a priorityof the packet and an operation of encrypting and transmitting the packetwhen an available resource amount is greater than a minimum threshold orless than a maximum threshold, and performing a non-encryptiontransmission on the packet when the available resource amount is lessthan the minimum threshold or greater than the maximum threshold. Aftera routine of verifying whether the value of the PB header counterparameter is the maximum value, a number of video packets present in thetransmission buffer may be counted. If the counted number of videopackets is a maximum value that may be included in a single IP packet, avalue of the priority parameter may be checked. When the value of thepriority parameter is a relatively high value, and when stateinformation of a resource use monitoring device or an external inputdevice represents a normal situation in which an available resourceamount is sufficient, video packets of the transmission buffer may betransmitted through an encryption protocol, for example, an SSLprotocol. In a situation in which the available resource amount isinsufficient, non-encryption transmission may be performed on the videopackets of the transmission buffer. When the value of priority parametervalue is a relatively low value, the video packets may be transmittedthrough a non-encryption protocol, for example, a TCP. If the number ofvideo packets present in the transmission buffer is not the maximumvalue, a subsequent video packet may be read from the reception buffer.

FIGS. 7 and 8 are flowcharts illustrating an operation of decoding apacket in an encrypted packet reception method of a communication systemaccording to an example embodiment.

In operation S710, whether decryption of a packet is required may bedetermined based on a packet identification criterion of the packet.Referring to FIG. 8 for understanding, a packet identifier may bedetermined based on the packet identification criterion and whether thepacket is encrypted may be determined. When the packet is an importantpacket having a relatively high priority requiring decryption,decryption of the packet may be performed. When the packet has arelatively low priority, an original order may be restored by retrievinga location of a corresponding frame header and the packet may be storedin a transmission buffer.

In operation S720, the packet may be decrypted when the decryption ofthe packet is determined to be required. According to an exampleembodiment, whether a type of the packet corresponds to a P-frame orB-frame header may be determined. When the packet corresponds to theP-frame or B-frame header, a structure for retrieving a location of anon-encrypted packet by restoring an original location may beconfigured. Otherwise, a packet may be stored in the transmission bufferin received order. Referring to FIG. 8, once the above process isterminated, a process of receiving a packet is repeated to read asubsequent packet. Received data may be transferred to an externaloutput device.

FIG. 9 is a block diagram illustrating a configuration of a packettransmission apparatus of a communication system according to an exampleembodiment.

Referring to FIG. 9, a packet transmission apparatus 900 of acommunication system may include a processor 910, an encoder 920, and atransmitter 930. The processor 910 may determine whether to perform apacket identification process or a packet encryption process based on aremaining system resource amount, and may identify the packet based on apacket identification criterion when the packet identification processand the packet encryption process are determined to be performed. Evenin this case, the packet identification criterion may be recognized asthe same concept as a packet ID on the communication system and mayindicate each of identifiers assigned to packets in a multiplexedtransmission flow, respectively. When multiplexing and transmitting aplurality of channel signals using a single transmission line, thecommunication system may independently compress and packetize each ofthe channel signals and then may multiplex packets and transmit themultiplexed packets. Here, the same packet identifier (PID) may beassigned to a packets corresponding to a single channel and bedistinguished from a packets of another channel.

The encoder 920 may rearrange frames of the packet based on a result ofidentifying the packet and may encrypt the packet in which the framesare rearranged. The transmitter 930 may transmit the encrypted packet.Once an identified specific packet is encrypted, encryption transmissionmay be performed by applying an encryption protocol, for example, an SSLprotocol, or an encryption algorithm, for example, an AES algorithm.Non-encryption transmission may be performed on a packet correspondingto a packet identification criterion that does not require encryptiontransmission. The packet rearrangement and encryption process is thesame as the aforementioned encrypted packet transmission method of thecommunication system and a further description is omitted.

FIG. 10 is a block diagram illustrating a configuration of a packetreception apparatus of a communication system according to an exampleembodiment. Referring to FIG. 10, a packet reception apparatus 1000 of acommunication system may include a processor 1010 and a decoder 1020.

The processor 1010 may determine whether decryption of a packet isrequired based on a packet identification criterion of the packet. Theprocessor 1010 may determine a packet ID based on the packetidentification criterion and may determine whether the packet isencrypted. When the packet is an important packet having a relativelyhigh priority requiring decryption, the processor 1010 may performdecryption of the packet. When the packet has a relatively low priority,the processor 1010 may restore an original order by retrieving alocation of a corresponding frame header and may store the packet in atransmission buffer.

When the decryption of the packet is determined to be required, thedecoder 1020 may decrypt the packet based on the packet identificationcriterion. The decoder 1020 may determine whether the packet correspondsto a P-frame or B-frame header and may configure a structure forretrieving a location of a non-encrypted packet by restoring an originallocation of a frame header when the packet corresponds to the P-frame orB-frame header. Otherwise, the decoder 1020 may store a packet in thetransmission buffer in received order. Referring to FIG. 8, once theabove process is terminated, a process of receiving a packet is repeatedto read a subsequent packet. Received data may be transferred to anexternal output device. According to another example embodiment, thepacket identification criterion may be associated with a level ofsecurity required for transmission of the packet. An importance of thepacket may be determined based on the required level of security andwhether to encrypt the packet may be determined based on the determinedimportance.

A number of example embodiments have been described above. Nevertheless,it should be understood that various modifications may be made to theseexample embodiments. For example, suitable results may be achieved ifthe described techniques are performed in a different order and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner and/or replaced or supplemented by othercomponents or their equivalents.

Accordingly, other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A packet transmission method of a communicationsystem, the method comprising: identifying a packet based on a packetidentification criterion; reallocating frames included in the identifiedpacket, and encrypting the packet in which the frames are rearranged;and transmitting the encrypted packet.
 2. The method of claim 1, whereinthe packet identification criterion is associated with headerinformation of the packet.
 3. The method of claim 2, wherein the headerinformation is compatible with at least one of a network abstractionlayer (NAL) header format of an H.264/advanced video coding (AVC)standard and a NAL header format of a high efficiency video coding(HEVC)/H.265 standard.
 4. The method of claim 2, wherein the headerinformation is compatible with a header format of an MPEG-2 transportstream (TS) standard.
 5. The method of claim 1, wherein the packetidentification criterion is associated with a level of security requiredfor transmission of the packet.
 6. The method of claim 1, wherein theencrypting comprises: reallocating locations of the frames so thatframes including a data area of the packet are positioned to be adjacentto each other among the entire frames included in a cross-referencerange; and storing the rearranged frames in a storage space for a frametransmission.
 7. The method of claim 1, wherein the identifying of thepacket based on the packet identification criterion comprisesdetermining a priority of the packet by verifying a value of an MPEG-2TS header and a value of a NAL header, and the reallocating of theframes and the encrypting of the packet comprises: verifying whether thepriority of the packet is greater than a desired value; and encryptingand transmitting the packet when an available resource amount is greaterthan a minimum threshold or less than a maximum threshold, andperforming a non-encryption transmission on the packet when theavailable resource amount is less than the minimum threshold or greaterthan the maximum threshold, in response to the priority of the packetbeing verified to be greater than the desired value.
 8. The method ofclaim 1, wherein the identifying of the packet based on the packetidentification criterion comprises determining a priority of the packetby verifying a value of an MPEG-2 TS header and a value of a NAL header,and the reallocating of the frames and the encrypting of the packetcomprises storing the packet in a transmission buffer when thedetermined priority is greater than a desired value and storing thepacket in a flush buffer when the determined priority is less than thedesired value.
 9. A packet reception method of a communication system,the method comprising: determining whether decryption of a packet isrequired based on a packet identification criterion of the packet; anddecrypting the packet based on the packet identification criterion whenthe decryption of the packet is determined to be required.
 10. Themethod of claim 9, wherein an identifier of the packet is associatedwith header information of the packet.
 11. The method of claim 9,wherein the packet identification criterion is associated with a levelof security required for transmission of the packet.
 12. A packettransmission apparatus of a communication system, comprising: aprocessor configured to determine whether to perform a packetidentification process or a packet encryption process based on aremaining system resource amount and to identify a packet based on apacket identification criterion when the packet identification processand the packet encryption process are determined to be performed; anencoder configured to rearrange frames of the packet based on a resultof identifying the packet and to encrypt the packet in which the framesare rearranged; and a transmitter configured to transmit the encryptedpacket.
 13. The packet transmission apparatus of claim 12, wherein theencoder is configured to rearrange locations of the frames so thatframes including data of the packet are positioned to be adjacent toeach other among the entire frames included in a cross-reference range,and the processor is configured to store the rearranged frames in astorage space for a frame transmission.
 14. The packet transmissionapparatus of claim 12, wherein the packet identification criterion isassociated with a level of security required for transmission of thepacket.